Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$219.39	4.729%	$229.765	$229.77	$229.75	$229.80
Purchase #2	$47.72	6.516%	$50.8294	$50.83	$50.85	$50.80
Purchase #3	$65.77	10.733%	$72.8291	$72.83	$72.85	$72.80
Purchase #4	$60.85	8.726%	$66.1598	$66.16	$66.15	$66.20
Purchase #5	$51.32	3.208%	$52.9663	$52.97	$52.95	$53.00
Purchase #6	$95.33	8.715%	$103.638	$103.64	$103.65	$103.60
Purchase #7	$79.45	9.582%	$87.0629	$87.06	$87.05	$87.10
7 purchase totals =	$619.83		$663.2505	$663.26	$663.25	$663.30